Color diffusion transfer processes generally involve the use of a photographic element comprising a support, at least one silver halide emulsion layer, and a dye-providing compound which is contained in or contiguous to said layer. The dye-providing compound is typically represented by the chemical structural formula of Car-Dye [wherein Dye represents a dye moiety or a precursor thereof, and Car represents a moiety which, as a function of silver development under an alkaline contdition, forms or releases a substance (dye compound) having a mobility different from that of the dye-providing compound, and can be thought of as a carrier which may be attached to the dye moiety optionally through a linking ground]. This Car moiety brings about the change in mobility of the dye compound in proportion to development and, with dye-providing compounds that are diffusion-resistant even under alkaline conditions, diffusible dyes are released in proportion to the degree of development (i.e. according to a progress of developement or reverse progress of development) or are rendered soluble in proportion to the degree of development, and thus diffusible. In contrast, with dye-providing compounds which are diffusible under alkaline conditions, the dyes are rendered insoluble in proportion to the degree of development, and thus non-diffusible. Typical examples thereof are dye developers.
As the typical examples of the former, there are dye-releasing redox compounds described in Japanese Patent Application (OPI) Nos. 33826/73 (corresponding to U.S. Pat. No. 3,928,312), 114424/74, 126331/74, 126332/74, 115528/75, 104343/76 (corresponding to U.S. Pat. No. 4,198,235), U.S. Pat. No. 3,954,476, Research Disclosure, 13024 (1975) and 16475 (1977). The term "dye-releasing redox compounds" as used herein means compounds wherein a group, called a redox parent nucleus (corresponding to the foregoing Car), and a dye moiety (including a precursor thereof) are attached to each other. The redox parent nucleus is initially immobilized by the function of a ballast group bound thereto and, upon redox reaction under alkaline conditions, undergoes cleavage to release a dye moiety-containing compound (dye compound). As a result, this dye compound diffuses into an image-receiving layer to form a transferred dye. (The term "OPI" as used herein refers to a published unexamined Japanese patent application.)
Of the redox parent nuclei, there are those which are called "positive-working" type described in, for example, Japanese Patent Application (OPI) Nos. 110827/78, 110828/78, 164342/81, etc. Some release dye compounds in an inverse gradation to that of developed silver, i.e., inverse imagewise.
As the dye-providing compounds, yellow dye-providing compounds, magenta dye-providing compounds, and cyan dye-providing compounds are known. Examples of the magenta dye-releasing redox compounds are described in Japanese Patent Application (OPI) Nos. 115528/75, 114424/74, U.S. Pat. Nos. 3932380, 3931144, etc.
However, magenta dye-releasing redox compounds described in the preceding literature have the disadvantages that they show a poor color reproducibility, since the magenta dye-releasing redox compounds provide transfer images having insufficient hue, that they provide dyes having insufficient diffusibility to cause prolonged image-completing time, that they lower the efficiency of light absorption of an underlying red-sensitive emulsion (leading to reduction in sensitivity), since their spectral absorption in a coat before photographic processing expands to a longer wave-length region, and that they provide transfer images having poor sharpness. For example, with respect to the hue of the transfer image, the maximum absorption wave-length (.lambda.max) and the foot shape of absorption spectrum are of importance. As to absorption shifted to a shorter wave-length side fails to present dark red, whereas absorption shifted to a longer wave-length side fails to present bright red. As to the foog shape of absorption spectrum, broad absorption spectrum at the foot portion can reproduce only a stained color. It has been difficult to develop magenta dyes having an absorption spectrum with both suitable .lambda.max and a good foot shape, by conventionally known techniques.
With respect to spectral absorption properties in coatings before photographic processing, conventionally known magenta dyes function as unfavorable filters for an underlying red-sensitive emulsion since they have a magenta color in the coatings, and therefore orange to yellow light rays of about 600 nm do not reach the red-sensitive emulsion. Thus, it is difficult to reproduce such color, and such color reduces sensitivity of red-sensitive emulsion and causes serious changes in color reproduction depending upon the color temperature of the light source used.
It has heretofore been eagerly desired to solve or overcome these problems or defects at the same time.
Japanese Patent Application (OPI) No. 4028/80 describes magenta dye-releasing redox compounds in which an amino group derivative is attached to a phenylene group bound to an azo group constituting a dye moiety and a redox parent nucleus is attached to the same phenylene group directly or through a linking group. The redox compounds are considerably excellent dye-providing compounds in that they form dyes that undergo less fading in darkness or by light, and they form dyes with good hue. However, this type of redox compounds have problems with synthesis adaptability and sharpness of the transfer dye image. Thus, these problems have been desired to be solved.